Conventional ac-induction-motors include rotors which surround or are surrounded by a stator. In a known design, the rotor includes a stack of identical and aligned steel rotor laminations each having an array of circumferentially spaced apart rotor slots. The rotor slots are filled with an aluminum alloy or copper. The rotor lamination is manufactured with closed slots. For some applications, the rotor lamination stack is machined to remove a small radial length of material to create open slots exposing the aluminum alloy or copper, wherein the slot opening has a small width, and wherein each rotor lamination in the machined stack may be referred to as a rotor lamination having open rotor slots. A slot designed for a stator is not suitable to be a slot designed for a rotor. A rotor slot design which improves motor performance for one motor application typically will not improve motor performance for at least one other motor application.
Existing open rotor slot designs dramatically increase the width of the slot opening with a very small increase in radial length of removed material resulting in large variations in the width of the slot opening in production rotors. For some motor applications, such as those motors receiving voltage from a DC (direct current) to AC inverter, large variations in the width of the slot opening will result in undesired variations in motor performance in production motors.
What is needed is an improved AC-induction-motor rotor lamination having rotor slots.